The known conventional methods of displaying stereoscopic images without using special glass are the lenticular method, the parallax barrier method, and a method in which a light source is formed in the shape of slits.
FIG. 4 is a schematic view showing the principle of stereoscopic image display based on the parallax barrier method. Images that an observer ca view are formed on a liquid crystal display panel 50. To realize stereoscopic vision, left-eye-pixels L for displaying images for the left eye and right-eye-pixels R for displaying images for the right eye are alternately arrayed on the liquid crystal display panel 50. For example, the left-eye-pixels L and the right-eye-pixels R can be obtained by simultaneously taking images using two cameras for the left eye and the right eye, or, alternatively, by calculating theoretically based on data pertaining to one image. Both pixels obtained in this manner contain parallax information necessary for a person to achieve stereoscopic perception by binocular parallax.
Alight-shielding parallax barrier 51 is arranged in front of the liquid crystal display panel 50. Openings 51a are formed on the parallax barrier 51 in the form of vertical stripes. Gaps between the openings 51a are set corresponding to the array of left-eye-pixels L and right-eye-pixels R. Images for the left eye and images for the right eye are separated into right and left by the parallax barrier 51, and the separated images severally enter the left eye 2L and right eye 2R of the observer, enabling him to view stereoscopic images.
A stereoscopic image display device according to the above-described liquid crystal parallax barrier method is disclosed in Japanese Laid-Open Patent Publication No. 3-119889, for example, and description will be made thereof hereafter, using FIG. 5.
FIG. 5 is a schematic cross-sectional view of a stereoscopic image display device 10 based on the parallax barrier method, which includes a liquid crystal parallax barrier arranged in front of a liquid crystal panel as an image display device. In FIG. 5, a transmissive liquid crystal panel 16, on which display pixels are arrayed via the first polarizing plate 14, is arranged on the surface of a backlight 12, while a liquid crystal parallax barrier 24 is further arranged via the second polarizing plate 18, the glass spacer 20 and the third polarizing plate 22, and the fourth polarizing plate 26 is arranged on the surface of the liquid crystal parallax barrier 24.
The transmissive liquid crystal panel 16 consists of a rear glass plate 16a located on the incident side of light, a front glass plate 16b located on the output side of light, pixel electrodes 16c formed on the inner side of the rear glass plate 16a, a color filter 16d formed on the inner side of the front glass plate 16b, and liquid crystal 16e filled and sealed between the rear glass plate 16a and the front glass plate 16b. Respective images for the right eye and the left eye are alternately displayed on the transmissive liquid crystal panel 16.
In the liquid crystal parallax barrier 24, liquid crystal 24c is inserted into the sealed space sandwiched between the two glass plates 24a, 24b, on the inside of which stripe-shaped electrodes and opposite electrodes (not shown) are respectively formed parallel with the stripes of the pixels L and R of the transmissive liquid crystal panel 16, and the barrier performs display of 2D images under a no voltage applied state and display of 3D images under a voltage applied state. Specifically, the liquid crystal parallax barrier 24 specifies its XY addresses by control means such as a microcomputer, and forms barrier stripes of an arbitrary shape at an arbitrary position on a barrier plane in the case of 3D display.
However, the barrier stripes in the form of vertical stripes are generated only when 3D images are displayed, and the drive of the barrier is controlled to arrest the generation of barrier stripes and to achieve a transparent and colorless state for the entire image display region when displaying 2D images.
The glass spacer 20 using a glass substrate is arranged as a spacer member between the liquid crystal panel 16 for display and the liquid crystal parallax barrier 24. The liquid crystal panel and the spacer member, and the spacer member and the liquid crystal parallax barrier are bonded by double-faced tape at the peripheral edge portions of the panel.
In the stereoscopic image display device, it is necessary to widen the gap between the liquid crystal panel 16 for display and the liquid crystal parallax barrier 24 as the screen of the display device becomes larger. Specifically, to observe displayed binocular parallax images, it is necessary to provide for a fixed range for the distance between the liquid crystal panel for display and the liquid crystal parallax barrier to obtain good stereoscopic images, and such distance must be increased as the distance between the observer and the screen becomes larger as a result of increase in screen size. In other words, the distance is shorter in the case of a small device applied to a cell phone, but naturally becomes larger when used in a TV set or the like.
As the means for adjusting the gap between the liquid crystal display panel and the liquid crystal parallax barrier, in the stereoscopic image display device described in Japanese Laid-Open Patent Publication No. 3-119889 publication, the glass substrate or acrylic plate serving as the spacer member is arranged between the liquid crystal display panel and the liquid crystal parallax barrier, and the gap between the liquid crystal display panel and the liquid crystal parallax barrier accordingly conforms to the thickness of the spacer member. The spacer member must either be a glass substrate or an acrylic plate because it must be capable of transmitting illumination light coming from the backlight.